Vasopressors and Inotropes/Chronotropes

This page should be read after / in conjunction with the Handbook page on SHOCK

Introduction

1. Inotropes and vasopressors are powerful drugs that are used to alter a patient’s heart rate, blood pressure and the force of cardiac contraction. They are most commonly used by Intensivists and Anaesthetists but are also seen on Medical and Surgical HDU and in ED Resus.
2. Any patient needing Critical Care interventions (any vasoactive drug below) MUST be discussed and agreed with the Consultant responsible.
3. Senior input is essential for ensuring appropriate management and escalation decisions/discussions.
4. Outwith ALS algorithms, decisions on ongoing vasopressor / inotropes in the 2222 situations should be decided with the ICU team.

Definitions

1. Inotropes are agents that alter cardiac contractility (force and rate).
2. Vasopressors are agents that cause vasoconstriction.
3. Chronotropes are agents that alter the heart rate.

Actions of the Main Drugs we Use in Dumfries

Which Drugs to Use?

1. Many agents have multiple effects, and to different degrees.
2. You MUST have some understanding of the cause(s) of shock to know which drug to use.
3. Remember: Not all shock is treated with vasopressors
4. The main drugs outwith/pending Critical Care admission or within HDU you will need to consider using are:

Noradrenaline (Norepinephrine)

1. This is the UK’s first-line vasopressor and will improve blood pressure by causing vasoconstriction in the EUVOLAEMIC VASODILATED patient.
2. There is some inotrope action as well – helpful in settings such as anaphylaxis or sepsis, or those with underlying reduced cardiac function.
3. Ensure the patient is volume replete first.
4. Noradrenaline requires a central venous catheter (CVC) so arrange for this early if you think you are going to need using Norad.
5. It should NOT be bolused.
6. Plans must be in place for CCU transfer. It may be started in ED Resus but CVC must be inserted first.
7. To prepare, make up one 4mg ampoule of Noradrenaline to 50ml of 5% Dextrose. This produces an 8% solution (80micrograms/ml), also known as ‘Single Strength’.
8. Generally start at 5ml/hr in a shocked patient and titrate the rate to target a Mean Arterial Pressure (MAP) of 60-65mmHg (but see point 10 below)
9. Review the patient to ensure end-organ perfusion (GCS/BP/UO) improves (and hopefully a reducing lactate as well).
10. Stroke, Brain Injury, Trauma, Paediatrics are specific settings that will require altered MAP targets – ask your consultant or ICU.

Metaraminol

1. It is a vasoconstrictor without inotropic action
2. It is best used in pure vasodilatory shock without any concern over cardiac function and as with Noradrenaline, should be used in the EUVOLAEMIC patient.
3. It is contraindicated if the patient is on a Monoamine Oxidase Inhibitor (such as Selegiline or Phenelzine)
4. It is peripherally administered
5. Outwith ED, this needs to be given in CCU unless Level 1 beds in D8 exist
6. It can be bolused in 1-2ml boluses of 0.5mg/ml concentration (1 x 10mg ampoule diluted into 20ml 0.9% saline)
7. Boluses may last up to approximately 20 minutes, less in the more unwell
8. More than one bolus should prompt the need for an infusion to be setup (20mg into 40ml 0.9% Saline, starting at 5ml/hr and titrate to response, max 10ml/hr)
9. Infusions should unless very short-term be long enough to organize CVC and Noradrenaline commencement in appropriate patients. Those not responding to Metaraminol in ED should have CVC and Noradrenaline started in ED to stabilize the patient concurrently with ICU referral for review.
10. If only boluses are being given pending CVC insertion, you MUST stay with the patient, including escorting to CCU in case more is needed – Cardiac arrest during transfer should be maximally avoided
11. Convert to Noradrenaline via CVC (where appropriate to escalate), or withdraw if inadequate response, within approximately 12 hours
12. Prolonged infusions should be avoided (evidence of harm from similar medicine (Phenylephrine) in Septic Shock)
13. Beware it can cause bradycardia and make the clinical situation worse

Isoprenaline

1. It is used for primary bradycardia that is compromising BP as a bridge to pacing (temporary or permanent).
2. This is a peripherally or centrally administered drug used ONLY after discussing with a consultant (preferably the cardiologist oncall).
3. It should NOT be bolused.
4. This needs to be given in CCU unless Level 1 beds in D8 exist
5. It is made up by adding 2mg Isoprenaline to 500ml of 5% Dextrose (final concentration 4micrograms/ml).
6. Start at a rate of 15ml/hr by volumetric pump, titrating up in 15ml increments every 2-3 minutes until target HR achieved (and watching for adverse effects as in point 9). Usual maximum = 150ml/hr.
7. Generally target a HR of 60-70 or enough to bring up BP / end organ perfusion.
8. All patients should be on cardiac monitoring / telemetry (preference) if not in CCU.
9. Be aware this medicine can cause vasodilation, arrhythmias and hypotension and the patient may need more specialist input (discuss with ICU).
10. Other indications for isoprenaline do exist but are outwith the remit of this document

Dobutamine

1. This can be given peripherally in low doses but in the acutely unwell patient, requires either Cardiology or ICU team input before commencing.
2. This needs to be given in CCU
3. It should be administered via CVC if one is already in place but can be given peripherally only by consultant direction.
4. If it is being used in combination with other vasoactive agents, this will likely require input from the ICU team therefore refer early.
5. It is made by diluting a 250mg 20ml ampoule up to 50ml in a syringe by using 30ml of 5% dextrose or 0.9% Saline (final concentration 5mg/ml).
6. Start at 2mls/hr and target adequate organ perfusion (as directed by Cardiology or ICU) including cerebral and/or MAP targets. Do not uptitrate quickly.
7. Be aware this medicine can cause vasodilation and tachycardias so if either will worsen the situation, or tachycardia is worsening, the patient will need more specialist input urgently (discuss with ICU) and the dobutamine infusion should not be increased further.
8. The specialist teams may alter the rate  following their involvement, appropriate investigation and/or monitoring.

All of these drugs are best looked after within the CCU environment so when it is deemed appropriate, ensure early liaison with the CCU Charge Nurse.

Refer to drug protocols on Beacon for more information – links below

Links

• Handbook Section on Shock
• Handbook Section on Bradycardias

Content by Dr Alex Mcdonald, Consultant in Acute Medicine and Critical Care & Alison Bell, Lead Pharmacist Acute & Diagnostics